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Tennis Arm Injury Epidemic

Tennis Arm Injury Epidemic

ARM INJURY EPIDEMIC

Two-time finalist is recovering from shoulder surgery. (Facebook)

Vera Zvonareva had surgery her right shoulder this week and won’t return for several months

THE ARM INJURY EPIDEMIC

8 OUT OF 10 TOP PLAYERS SUFFER MULTIPLE ARM INJURIES OR SURGERIES: 1

34 OF TOP 40 ATP AND WTA PROS SUFFERED RETIREMENT FROM 117 MATCHES DUE TO ARM INJURY. 2

Player Current Rank injury date of injury (by (as of 2-2014) week) 1 Mens Left shoulder tendinitis 45/2010 - 47/2010 Rafael Nadal 1 Mens Arm 33/2007 - 35/2007 Rafael Nadal 1 Mens Shoulder 24/2006 - 25/2006 Rafael Nadal 1 Mens Shoulder (doubles) 42/2004 - 52/2004 Rafael Nadal 1 Mens Shoulder 21/2003 - 25/2003 2 Mens Shoulder 45/2011 - 47/2011 Novak Djokovic 2 Mens Sore right shoulder 33/2011 - 35/2011 Novak Djokovic 2 Mens Shoulder 5/2011 - 8/2011 Stanislas Wawrinka 3 Mens Left Shoulder 5/2006 - 5/2006 4 Mens Right shoulder 29/2010 - 33/2010 David Ferrer 4 Mens Shoulder (doubles) 19/2006 - 19/2006 Juan Martin del Potro 5 Mens Shoulder 45/2011 - 2/2012 Juan Martin del Potro 5 Mens Wrist 6/2010 - 2/2011 Juan Martin del Potro 5 Mens Wrist 2/2010 - 3/2010 Juan Martin del Potro 5 Mens Wrist 41/2009 - 45/2009 Tomas Berdych 6 Mens Right shoulder 34/2013 - 35/2013 Tomas Berdych 6 Mens Left wrist 6/2013 - 8/2013 Tomas Berdych 6 Mens Right shoulder 17/2012 - 19/2012 Tomas Berdych 6 Mens Right shoulder 35/2011 - 37/2011 Tomas Berdych 6 Mens Right shoulder 33/2011 - 35/2011 7 Mens Elbow 16/2011 - 18/2011 Andy Murray 7 Mens Wrist 7/2011 - 15/2011 Andy Murray 7 Mens Left wirst 40/2009 - 44/2009 Andy Murray 7 Mens Wrist 20/2007 - 32/2007 9 Mens Shoulder 5/2011 - 8/2011 Richard Gasquet 9 Mens Shoulder 12/2009 - 16/2009 Richard Gasquet 9 Mens Right shoulder 7/2009 - 8/2009 Richard Gasquet 9 Mens Right elbow 44/2008 - 1/2009 Richard Gasquet 9 Mens Elbow 21/2006 - 21/2006

1 See http://tennis.matchstat.com/AllInjuries/ 2 Id. Richard Gasquet 9 Mens Wrist 12/2004 - 14/2004 Jo-Wilfried Tsonga 10 Mens Right arm (doubles) 33/2011 - 35/2011 Jo-Wilfried Tsonga 10 Mens Right arm 32/2011 - 33/2011 Jo-Wilfried Tsonga 10 Mens Wrist 44/2009 - 45/2009 Jo-Wilfried Tsonga 10 Mens Right Arm 26/2005 - 5/2006 11 Mens Right shoulder 41/2010-52/2010 Tommy Haas 12 Mens Shoulder 32/2013-33/2013 Tommy Haas 12 Mens Shoulder 41/2009-42/2009 Tommy Haas 12 Mens Shoulder 17/2008-24/2008 Tommy Haas 12 Mens Right shoulder 3/2008-8/2008 Tommy Haas 12 Mens Right shoulder 19/2007-26/2007 Tommy Haas 12 Mens Wrist 15/2006-21/2006 Tommy Haas 12 Mens Shoulder 9/2006-9/2006 13 Mens Shoulder (doubles) 29/2011-31/2011 John Isner 13 Mens Shoulder 31/2010-33/2010 15 Mens Right Elbow 44/2013-2/2014 Mikhail Youzhny 15 Mens Wrist 3/2010-6/2010 16 Mens Wrist 41/2013-3/2014 Tommy Robredo 16 Mens Wrist 10/2009-12/2009 Nicolas Almagro 17 Mens Wrist 28/2008-35/2008 Nicolas Almagro 17 Mens Right wrist 19/2008-22/2008 Nicolas Almagro 17 Mens Right Elbow 37/2007-42/2007 Nicolas Almagro 17 Mens Right Shoulder 40/2004-45/2004 19 Mens Right Arm 29/2013-32/2013 20 Mens Arm 2/2009-6/2009 Agnieszka Radwanska 3 Womens Right shoulder 21/2013 - 25/2013 Agnieszka Radwanska 3 Womens Right shoulder 34/2012 - 35/2012 Agnieszka Radwanska 3 Womens Right elbow 9/2012 - 10/2012 Agnieszka Radwanska 3 Womens Right shoulder (doubles) 32/2011 - 34/2011 Agnieszka Radwanska 3 Womens Right hand 34/2009 - 35/2009 Agnieszka Radwanska 3 Womens Right forearm 24/2008 - 25/2008 Agnieszka Radwanska 3 Womens Right wrist strain 20/2007 - 21/2007 4 Womens Right shoulder 20/2012 - 22/2012 Victoria Azarenka 4 Womens Right hand strain 32/2011 - 35/2011 Victoria Azarenka 4 Womens Right elbow contusion 19/2011 - 21/2011 Victoria Azarenka 4 Womens Shoulder 16/2011 - 17/2011 Victoria Azarenka 4 Womens Right shoulder 31/2010 - 33/2010 Victoria Azarenka 4 Womens Right shoulder 14/2009 - 17/2009 Victoria Azarenka 4 Womens Right shoulder 42/2008 - 1/2009 5 Womens Right shoulder 34/2013 - 1/2014 Maria Sharapova 5 Womens Right elbow 11/2010 - 19/2010 Maria Sharapova 5 Womens Right shoulder 31/2008 - 20/2009 Maria Sharapova 5 Womens Right shoulder 25/2008 - 26/2008 Maria Sharapova 5 Womens Right shoulder 40/2007 - 45/2007 Maria Sharapova 5 Womens Shoulder 14/2007 - 21/2007 6 Womens Left shoulder 29/2010 - 31/2010 Angelique Kerber 6 Womens Right wrist 19/2008 - 24/2008 Angelique Kerber 6 Womens Shoulder 10/2008 - 11/2008 7 Womens Left shoulder 29/2010 - 31/2010 Simona Halep 7 Womens Right wrist 19/2008 - 24/2008 Simona Halep 7 Womens Shoulder 10/2008 - 11/2008 Jelena Jankovic 8 Womens Wrist 39/2009 - 42/2009 Jelena Jankovic 8 Womens Right forearm 24/2008 - 26/2008 Petra Kvitova 9 Womens Elbow 14/2009 - 16/2009 10 Womens Right shoulder 30/2011 - 31/2011 Sara Errani 10 Womens Right shoulder 20/2011 - 21/2011 Sara Errani 10 Womens Right shoulder 27/2010 - 28/2010 Sara Errani 10 Womens Right shoulder 42/2009 - 2/2010 Sara Errani 10 Womens Right arm 38/2009 - 39/2009 Sara Errani 10 Womens Right shoulder 8/2009 - 14/2009 Sara Errani 10 Womens Shoulder 29/2008 - 30/2008 11 Womens Right shoulder 1/2014-2/2014 Caroline Wozniacki 11 Womens Shoulder 27/2011-34/2011

Ana Ivanovic 12 Womens Left wirst (doubles) 32/2011-33/2011 12 Womens Left wrist (doubles) 23/2011-24/2011 Ana Ivanovic 12 Womens Left wrist 20/2011-23/2011 Ana Ivanovic 12 Womens Shoulder 6/2010-12/2010 Ana Ivanovic 12 Womens Right hand 32/2008-35/2008 Dominika Cibulkova 13 Womens Right elbow 33/2012-34/2012 Dominika Cibulkova 13 Womens Right shoulder 27/2010-30/2010 14 Womens Right shoulder 18/2013-20/2013 Roberta Vinci 14 Womens Right wrist 41/2012-43/2012 Roberta Vinci 14 Womens Right wrist 21/2012-22/2012 Roberta Vinci 14 Womens Right elbow (doubles) 17/2011-18/2011 Roberta Vinci 14 Womens Wrist 27/2009-28/2009 Roberta Vinci 14 Womens Shoulder 6/2008-15/2008 Carla Suarez Navarro 15 Womens Right elbow 37/2011-38/2011 Carla Suarez Navarro 15 Womens Right elbow 8/2011-23/2011 Carla Suarez Navarro 15 Womens Right elbow 7/2009-8/2009 16 Womens Right wrist 30/2013-34/2013 Sabine Lisicki 16 Womens Rught shoulder 31/2009-35/2009 Sabine Lisicki 16 Womens Right shoulder 28/2009-30/2009 Sabine Lisicki 16 Womens Shoulder 18/2009-25/2009 17 Womens Right arm 31/2010-34/2010 18 Womens Left wrist 38/2011-2/2012 20 Womens Right wrist 28/2010-38/2010

95 TOP ATP PROFESSIONALS ARE CURRENTLY SIDELINED BECAUSE OF ARM INJURY. 3

Of the top 100 ATP professionals, in just the past 6 months, there were 28 matches retired due to arm, wrist, elbow, and shoulder pain. This does not account for all of the matches where they just played through the pain or those who didn't play at all. Amongst these pros racquets were played with the most (10) with coming in at a close second (8). Head racquets also had the most shoulder injuries at 6. Below is the complete listing.4

3 see http://www.tennisinsight.com/injuries.php 4 http://www.tennisinsight.com/injuries.php Player Type of injury Date of injury Model of racquet Manufacturer Left shoulder Feb 24 2014 Head YOUTEK Radical Midplus Head Shoulder Feb 17 2014 VCORE 95 Yonex Filippo Volandri Shoulder Feb 17 2014 Head YOUTEK IG Prestige Midplus Head Shoulder Feb 17 2014 Babolat Pure Control Babolat Roberto Bautista Agut Right wrist Feb 3 2014 Wilson Six.One 95 BLX (16x18) Wilson Aleksandr Nedovyesov Right shoulder Feb 3 2014 Babolat pure drive Babolat Bradley Klahn Wrist Jan 27 2014 Head YOUTEK IG Speed Head Arm Jan 20 2014 Babolat AeroPro Drive Babolat Bradley Klahn Wrist Jan 20 2014 Head YOUTEK IG Speed Head Tommy Haas Shoulder Jan 13 2014 Head YouTek IG Prestige Midplus Head Nicolas Almagro Shoulder Jan 13 2014 Dunlop Biomimetic Tour 500 Pro Dunlop Tommy Robredo Right arm Dec 28 2013 Dunlop Biomimetic M6.0 Dunlop Mikhail Youzhny Right elbow Oct 28 2013 Head YouTek IG Extreme Pro Head Pablo Andujar Right elbow Oct 28 2013 Prince EXO3 Tour 100 Prince Right elbow Oct 28 2013 Head YOUTEK Graphene Speed MP Head Aleksandr Nedovyesov Right elbow Oct 28 2013 Babolat pure drive Babolat Gael Monfils Left wrist Oct 28 2013 Wilson Blade 98 (18x20) Wilson Tommy Robredo Wrist Oct 6 2013 Dunlop Biomimetic M6.0 Dunlop Right wrist Sep 30 2013 Babolat AeroPro Drive Babolat Nikolay Davydenko Wrist Sep 23 2013 Babolat AeroPro Drive Babolat Janko Tipsarevic Right wrist Sep 16 2013 TFight 325 TP ATP Tecnifibre Michal Przysiezny Right shoulder Sep 2 2013 Wilson Blade 98 (18x20) Wilson Tomas Berdych Right shoulder Aug 18 2013 Head YouTek IG Instinct Head Tommy Haas Shoulder Aug 5 2013 Head YouTek IG Prestige Midplus Head Vasek Pospisil Shoulder Aug 5 2013 Wilson Six.One 95 BLX (16x18) Wilson Benoit Paire Elbow Jul 15 2013 Babolat AeroPro Drive Babolat Jerzy Janowicz Right arm Jul 15 2013 Babolat Pure Control Tour Babolat Mikhail Kukushkin Right shoulder Jul 8 2013 Head YOUTEK Graphene Speed MP Head

Caroline Wozniacki headlines a growing list of already‐injured players in 2014 [Updated] ATP, Injuries, WTA | Comments

Caroline Wozniacki tweaked her shoulder before leaving for . (Atsushi Tomura/Getty Images)

The 2014 tennis season has barely begun, yet the list of the injured and ailing has grown with each passing day. The most high-profile injury concern belongs to the newly-engaged Caroline Wozniacki, who was forced to withdraw from the with a right shoulder injury. Wozniacki felt the pain after her last practice before flying to Australia to start the season, but she ‘s still optimistic she will be able to play next week’s Sydney International.

TENNIS ICONS SUFFER TEMPORARY OR PERMANENT RETIREMENT FROM TENNIS AND THIS IS DEVASTATING FOR THE SPORT OF TENNIS.

RECENTLY CLISTERS and RODDICK RETIRED FROM SHOULDER INJURY. FROM ELBOW INJURY. SHARAPOVA, MURRAY and JUAN DEL POTRO SUFFERED TEMPORARY RETIREMENT

Half of all debilitating professional injuries are arm injuries. At any given time over 30% of top players are sidelined from arm injury. 80% of professional men and women have suffered arm injury or surgery. The industry cannot continue to avoid the issue.

ANDY RODDICK RETIRES FROM SHOULDER INJURY AFTER SURGERY- Roddick had suffered a knee injury in 2009, which set him back in training, and endured a serious shoulder surgery following his Wimbledon loss in 2010. Later that year, he announced that he had mononucleosis, a viral infection that includes symptoms similar to that of the flu. Around the same time, he experienced a groin and separate shoulder injury. In August 2012, 30-year-old Roddick announced plans to retire from tennis. Henin Says She Is Retiring for Good With Elbow Injury

By CHRISTOPHER CLAREY

Published: January 26, 2011 http://www.nytimes.com/2011/01/27/sports/tennis/27henin.html?_r=0

Azarenka withdraws from with shoulder injury

By Simon Cambers

Wed May 16, 2012 6:58pm EDT

(Reuters) - World number one Victoria Azarenka suffered a blow to her preparations when she was forced to pull out of the with a right shoulder injury.

Del Potro Sidelined by Surgery on Wrist

By CHRISTOPHER CLAREY

Published: May 4, 2010

Injury forces Agnieszka Radwanska out of New Haven By Jim Fuller special to EmiratesUSOpenSeries.com

NEW HAVEN ‐ For more than a set on Tuesday evening Agnieszka Radwanska’s shoulder was speaking just one word to her: No.

Sharapova, Citing Shoulder Injury, Will Miss Open

Ronald Martinez/Getty Images

Maria Sharapova has played only one match on tour since her second-round loss at Wimbledon in June.

By BEN ROTHENBERG

Published: August 21, 2013

Nadal to take time out to rest recurring shoulder injury after By Sportsmail Reporter UPDATED: 17:45 EST, 29 December 2011

Tennis - Steve Darcis undergoes shoulder surgery and to miss at least four months Tennis - Darcis shocked Rafael Nadal in Wimbledon first round

Tennis Stories 11 Oct 2013 - 11:28 / by Prakash / reads 668. Source:

Victoria Azarenka out in Rome Updated: May 17, 2012, 5:55 PM ET

Associated Press

ROME -- Top-ranked Victoria Azarenka has withdrawn from the Italian Open because of a right shoulder injury.

David Ferrer was then supposed to play in the 2010 International German Open as the second seed, but had to withdraw due to a shoulder injury.

Unfortunately my old shoulder injury flared up before the match and I had to retire from the tournament. My Life,

Sam Querrey Pulls Out of 2011 U.S. Open To Recover from Elbow Injury By Diana Sir Louis , Contributor Aug 20, 2011

Wimbledon 2011: Elbow injury strikes cruel blow for

Wednesday 22 June 2011 13.46 EDT

Heather Watson feels the pain from the elbow injury which reduced the effectiveness of her . Photograph: Julian Finney/Getty Images Andy Murray: “I had shoulder and elbow surgery while I was playing and I can remember what a frustrating time it was."

Novak Djokovic pulls out of with shoulder injury

Novak Djokovic has pulled out of the Paris Masters ahead of his scheduled quarter‐final against Jo‐Wilfried Tsonga, citing inflammation in his right shoulder.

Feeling the strain: Novak Djokovic has pulled out of the Paris Masters with a shoulder injury Photo: REUTERS

By Simon Briggs

10:59AM GMT 11 Nov 2011

Injured Berdych to miss

Updated Mar 29, 2013 1:15 PM ET

PRAGUE (AP) Tomas Berdych has a shoulder injury and will miss the defending 's Davis Cup quarterfinal against next month.

Ice on Shoulder

Arm-related injuries to marquee players in 2012 included Vera Zvonareva (shoulder), (shoulder), (shoulder), FlaviaPennetta (wrist), and JelenaDokic (wrist),

Barthel retires from Bad Gastein with shoulder injury Wednesday, July 17, 2013 /by AP

AP Photo

BAD GASTEIN, Austria (AP)—Top-seeded of pulled out with a shoulder injury while trailing 6-2, 4-3 to the 725th-ranked Lisa-Maria Moser in the second round of the Gastein Ladies on Wednesday.

Playing in her first WTA event, Moser broke twice to take the opening set and the Austrian wildcard was a break up in the second when the 31st-ranked Barthel withdrew.

Barthel, who was looking to reach her fourth quarterfinal of the season and first since winning in Paris in February, took over the top seeding after defending champion Alize Cornet of pulled out with a shoulder injury.

Haas retires with bad shoulder in Brazil semis

Jelena Dokic thought career was over after wrist surgery in 2012 Tennis Guru November 1, 2013 Tennis Feature, Tennis News, WTA No comments

Italy's retires due to wrist injury

Flavia Pennetta: Retired four games into her match against at with a right wrist injury. That’s the same wrist that required surgery and kept her out of most of the 2012 season. Date

January 2, 2014

Brad Elborough

Read more: http://www.smh.com.au/sport/tennis/italys‐flavia‐pennetta‐retires‐due‐to‐wrist‐injury‐ 20140102‐30862.html#ixzz2ulK6spoC

World No.10 Jo‐Wilfried Tsonga suffering a wrist injury

 By Leo Schlink  Herald Sun  December 31, 2009 10:24AM

World No.10 Jo-Wilfried Tsonga is struggling to be fit for the Australian summer circuit after injuring his wrist.

Sabine Lisicki Withdraws From Pattaya Open Citing a Shoulder Injury

Canadian tennis player Aleksandra Wozniak out with shoulder injury

Canadian tennis player Aleksandra Wozniak will be out of action for three months due to a right shoulder injury.

Injury beats Melzer PARIS: Austria's world No.27 Jurgen Melzer on Saturday withdrew from the Australian Open with a shoulder injury.

Read more: http://www.smh.com.au/sport/tennis/tsonga‐in‐form‐20140105‐ 30c1m.html#ixzz2ullFURbe

Brian Baker's comeback story gets better and better Updated 6/28/2012 11:55 AM WIMBLEDON, England (AP) – There were plenty of low points along the way back to tennis' biggest stages for Brian Baker. None worse, perhaps, than waiting to have reconstructive surgery on his right elbow in February 2008.

Vera Zvonareva has shoulder surgery WTA | Comments

Lleyton Hewitt retires against Marinko Matosevic in second round at

Posted Thu 20 Feb 2014, 2:57pm AEDT

Australia's number one Lleyton Hewitt was forced to retire after one set of his second-round clash with countryman Marinko Matosevic at the Delray Beach Open on Thursday (AEDT).

The eighth-seeded Hewitt, who won the inaugural tournament in 1999, dropped the first set 7-6 (7/2) against world number 55 Matosevic before pulling out with a shoulder injury prior to the first of the second.

ANGELIK KERBER

CONSUMER SAFETY AND INJURY

According to Keith Story of the Tennis Industry Association of America, 1.8 million recreational tennis players in the United States quit playing tennis altogether in 2011 due to an arm injury. 5. The Sports Marketing Surveys USA for the Tennis Industry Association reported 10% were from shoulder injury, 7% elbow injury and 5% “arm” injury.

The same TIA study reported in addition to those who quit tennis permanents, of those who stayed in the game, 30% also suffered injury.6 See Exhibit B attached.

According to International Tennis Federation (ITF), the governing body of the sport, half of all players will suffer elbow injury.7

Since the advent of composite racquets 30 years ago, over 150 million players have suffered a wrist, elbow or shoulder injury, according to Mark Kovacs, executive director of the International Tennis Performance Association (ITPA), a global sports science organization that focuses on the game of tennis. Kovacs says the 150 million figure was reported at the International Tennis Federation World Conference in Cairo in November, 2011.

This epidemic did not exist in these vast numbers prior to the advent of hollow, empty or air injected carbon rackets.8

5 Keith Storey, Sports Marketing Surveys USA for the Tennis Industry Association (10% from shoulder injury, 7% elbow injury and 5% “arm” injury)

6T I A S T A T E O F T H E I N D U S T R Y K e y T e n ni s I n d u s t r y I n d i c a t o r s 2 0 11 page 6 (30% of frequent players reported playing less tennis because of health or injury)

7http://www.itftennis.com/scienceandmedicine/injury‐clinic/tennis‐injuries/tennis‐elbow. The ITF’s website states:

“Tennis elbow is the best‐known and also the most painful elbow injury in tennis players. An estimated 50% of all tennis players will suffer from tennis elbow in the course of their career. Players aged over 35 are particularly at risk. . .The pain may radiate into the arm, wrist and fingers. The injury usually develops gradually, as a result of multiple micro ruptures and scar tissue at the muscle attachment. .. Tennis elbow is a common complaint, but as yet, there is no consensus on the optimal treatment strategy.”

Tennis elbow is an injury. “Injury is the damage sustained by tissues of the body in response to physical trauma.” W, Zernicke R. Biomechanics of musculoskeletal injury. page 2 Champaign, IL: Human Kinetics, 1998 Tennis elbow (or “Lateral epicondylitis”is caused by either abrupt or subtle injury of the muscle and tendon area around the outside of the elbow that damages the tissues. Beasley VidalLS, et al. (2007). Shoulder injuries. In PJ McMahon, ed., Current Diagnosis and Treatment in Sports Medicine, pp. 118‐145. New York: McGraw‐Hill. 8 All composite rackets have been made using air injected rackets. 8. Knudson D. Biomechanical research into tennis elbow. Proceedings of ISEA. ISEA 2004.

One upper-limb chronic injury afflicting tennis players is osteoarthritis. Osteoarthritis is the progressive loss of articular cartilage, which begins with fraying, or fibrillation, of the articular surface and progresses to exposure of the subchondral bone. Radiographic images were obtained of both shoulders and the results showed that 33% of tennis players had osteoarthritic changes in their dominant shoulder. 9 Degeneration of the dominant shoulder acromioclavicular joint was 55.5% in the studied group.10

A 1989 study shows that 50% of injuries are reoccurrences.11

The reported incidence of wrist injuries is higher among females (15.7% of all tennis injuries) than male players (11.2%).12

A 1989 Danish study shows that of all injuries 45% were upper limb injuries, 17% shoulder.”13

In 2003, out of 100,000 tennis players there were 21,300 injuries that required a doctor’s visit and 1,228 injuries that were serious enough to require hospitalization or surgery.14

According to Monash University 69% of adult tennis injury cases and 40% of child injury cases occurred during formal competition.Forty-five percent of all child tennis injuries in formal play were to the upper extremities. The public exposure of professional tennis and the vast amount of money involved has impacted upon young tennis players, leading to great pressure to practice, high expectations of performance and increasing demands on the human body (Mothadi and Poole 1996). More females (57%) than males (43%) play tennis.Over one-third (37%) of players are over the age of 45 years. Over one-half of all participants (55%) indicated that they participate in tennis once a week.In adult tennis players the upper limbs accounted for 24% of all injuries.Upper limb injuries were more common than lower limb injuries among children.15

Wrist injuries have become an increasing common problem since the modern game involves a higher combination of powerful serves and topspin forehands that now account for 75% of all strokes, according to Sports Medicine & Rehabilitation (2009).

9British Journal of Sports Medicine 2006; 40:447-450 10Am J Sports Med, 1997; 25:809-812 11Archives of Internal Medicine, vol. 149(11), pp. 2561-2564, 1989 12http://www.sportsinjurybulletin.com/archve/tennis-wrist-injuries 13Winge S, Jorgensen U, Lassen Nielsen A, ‘Epidemiology of injuries in Danish championship tennis’ Int J. Sports Med 1989 Oct; 10(5): 368-71 14http://www.democraticunderground.com/discuss/duboard.php?az=view_all&address=364x401653 15Monash University Accident Research Centre – Report #144 - 1999 Research conducted found that 70% of children in intensive tennis training programs suffered arm injury, permanent injury or arm surgery before the age of 16. Thousands of these young victims were especially vulnerable because of their underdeveloped tendons and muscles. The medical examinations from doctors concluded that the cause of the injury was the racket. see Adam Johnson medical diagnosis CPSC report.

Many children training under 10 serve underhand due to inability to lift the arm above the shoulder from permanent shoulder damage.

The Epidemic is reaching younger and younger children. The Childrens Hospital of Philadelphia, in Pennsylvania performs hundreds of surgeries on tennis kids every year.

A player survey at an WTA Tournament in the Bronx uncovered that 50% of players had undergone surgery before the age of 16.

Children as young as 8-years-old are hitting balls four to five hours a day, and modern composite racquets have “added too much power and put enormous wear and tear on young bodies,” wrote tennis legend in an article entitled, “Sidelined in their Prime” that appeared in the Jan. 9, 2009 edition of Newsweek. “More injuries are likely,” she warned, “unless tennis's governing bodies modify the [large numbers of tournaments on the] calendar and fight back against the racquet manufacturers that have hijacked the game.”

Twenty percent of junior players suffer from repetitive stress, compared to just 7.5 percent of professional players,. 16

BETHANIE MATTEK SANDS MIXED DOUBLES CAHMPION

“The racquets do contribute obviously to injuries. Because with the hollow racquets you’ll end up feeling more of the vibration up your arm. Kids have gotten younger and younger with more severe injuries‐ 10, 11, 12 year old kids potentially getting surgeries. To me it’s just crazy To see kids doing rehab as much as they are taping their shoulders, and the elbow bands. Hopefully that sparks some attention that there needs to be a change”.

16see British Journal of Sports Medicine.40(5), 454-459, 2006. See also Patricia Kolowich, MD, on the website, StopSportsInjuries.org

Current Equipment is Illegal under the CPSC rules

Enclosed is the CONSUMER SAFETY PRODUCT COMMISSION PRODUCT RECALL HANDBOOK

CPSC Product Recall Handbook Defines Class B and C Hazard as

Class B Hazard

Exists ... when...moderate injury ... is very likely.

Class C Hazard

Exists ...when moderate injury.. is not necessarily likely, but is possible.

Regardless of whether a product defect is classified as a Class A, B, or C priority hazard, the common element is that each of these defects creates a substantial product hazard that requires corrective action to reduce that risk of injury.

The priority given to a specific product defect provides a guideline for determining how best to communicate with owners and users of the defective product and to get them to respond appropriately. While some companies have exemplary track records in communicating with consumers independently, it is still to a company's advantage to work with the Commission staff, using both the company's and the Commission's skills and resources to conduct an effective product recall.

Regardless of which defect or combination of defect and mechanics aggravating the underlying cause of the injuries, if the result is a HAZARD under the rules, corrective action must be taken.

The CPSC as already begun investigations into the high rate of tennis arm injuries and could even ban the format of the sport as it exists today. All other industries involving products intended to be children are already regulated by the Consumer Safety product commission including Helmets, bats, Skis, snowboards, skateboards, etc. It is only a matter of time when tennis rackets will also require safety standards.

All current empty, hollow, or air injected rackets shock longer than .2 sec at impact and are illegal under CPSC rule 1115 and hazardous to the consumer population, should subject to CPSC regulation, consumer warning labels, standards and recall due to the high likelihood (well over 50%) of procuring injury. See 16 C.F.R. § 1115.

4. Failure to use known technology to prevent injury is negligent and subject to punitive damages. Under product liability law, once technology exist to prevent injury, if it is not used, it can subject parties to punitive damages. See Prosser, Handbook on the law of Torts. sec 7.04 8.04 (Failure to use known safety features is a basis for product liability).

Early cases involving seat belts found the automobile companies liable for not using known safety technology whenever there is a "foreseeable risk of harm". This DUTY OF CARE TO THE CONSUMER is elevated when the foreseeable end users are minors under the age of 16. As the game of tennis demands more rigorous physical endurance the number of children and juniors in training camps around the world have grown to numbers in the millions all vunerable if safety technology is not mandatory, required and strictly enforced.

"An injured test consumer can recover on the theory that the product would have been safe had the manufacturer incorporated safety features that were known at the time of product was designed." see Product Liability - Legal Dictionary

This is not a cause based theory of liability but rather a prevention based duty of reasonable care to the consumer.

RACKET SHOCK IS THE CAUSE

The paramount authority Dr Stuart Miller, the ITF’s Head of Science & Technical Commission, after years of studying all possible causes of the injuries concluded in a 2006 issue of British Journal of Sports Medicine that racket shock is the cause of injuries:

“By allowing the racket to be swung faster, the decrease in mass generates greater shock to the hand for impacts that are not at the centre of percussion. On the basis of a review of biomechanical evidence, it has been concluded that shock is the most likely cause of tennis elbow. 17

“The combination of the increased stiffness of modern rackets and the tendency for tennis balls to have become harder has led to an increased shock transmission from the racket to the player.18

“Although modern racket technology has produced many positive effects, it is arguable that injury rates have increased as a result. . .Anecdotal evidence suggests that the vast majority of upper limb injuries are chronic; having been developed over time through repetition….it is not unreasonable to suggest that the trend for increased power is responsible for the increased number of injuries seen in today's game. “19

“The ball leaves the strings before even the stiffest racquets can recoil, so most all the energy in the shock wave stresses the racquet and arm and does not return to the ball,”20. “After the ball has left the strings the player's arm is beginning to experience not only the forces of the shock wave, but also forces of racquet vibrations. “21

The fact that racket shock is the culprit is well supported.

The racket is a primary cause for the elbow to endure “the perfect storm”.22

17 Miller, Modern tennis rackets, balls, and surfaces Br J Sports Med. 403 (May 2006) 18 Id at 401 19 Id. 20 Dr Duane Knudson, Associate Professor, Department of Physical Education & Exercise Science, California State University 21 Id. Henning, Influence of racket properties, Id

22 David Bayliff Physical Therapist, MPT.

This epidemic did not exist in these vast numbers prior to the advent of light air injected rackets.23

In Influence of Racket Properties on Injuries and Performance in Tennis , Dr. Henning concludes that the characteristics of the racket causes racket shock.24

“Racket properties may affect tennis elbow development. Shock and vibration to the arm is influenced by the location of ball impacts on the racket head, racket stiffness, and grip force. Beginners experience increased arm loads, and they hit the ball lower on the racket head. Tennis rackets behave differently during actual play compared with the performance predicted by physics”

Stated RacquetResearch.com: “Poor stroking technique is frequently accused, conveniently diverting scrutiny from racquet design, but, as the calculations on this site prove, risk factors for tennis elbow include: (1) light racquet weight and (2) head-heavy balance. Stiff frames are also bad. What is good for minimizing elbow damage is low Shock, low Elbow Crunch, low Torque, and low Moment.

Shock in biomechanical load will cause stress and injury to muscle, tissues and tendons25.

REMEDIES

MINIMUM SAFETY CHARACTERISTICS OF RACKETS

23 Miller, All composite rackets have been made using air injection.. 8. Knudson D. Biomechanical research into tennis elbow. Proceedings of ISEA. ISEA 2004.

24 Exercise & Sport Science Review. 2007 Apr;35(2):62‐6. 15 Miller, All composite rackets have been made using air injected rackets. Knudson D. Biomechanical research into tennis elbow. Proceedings of ISEA. ISEA 2004.

Numerous studies have shown that the characteristics of the racket affect the shock load up to 5 times depending on the construction of the rackets.26

Old wooden rackets vibrate at about 90 Hz,3 whereas modern rackets can be made to vibrate at frequencies up to 200 Hz.”27 In the old wood rackets, vibration disappeared quickly because it was dampened by the flex of the solid wood, but the new stiffer, lighter and hollow conventional frames do a poor job of snuffing out the vibrations, so they transfer this shaking to the arm that can stealthily sabotage the elbow, wrist, forearm and shoulder. 28

In Transfer of tennis racket vibrations onto the human forearm., Hennig reported that “Between different racket constructions, almost threefold differences in acceleration values could be observed.” 29

The most recent study conducted by the Othrokinetic Labs showed that modern air injected or hollow rackets have shock duration up to 5 times that of a solid-core racket.

26Influence of Racket Properties on Injuries and Performance in Tennis , Henning concludes that it is the characteristics of the racket which causes racket shock. abstract abstract 20 20

1 false

27 . 8. Knudson D. Biomechanical research into tennis elbow. Proceedings of ISEA. ISEA 2004.

28 Orthokinetic labs

29 . “ One of several factors suspected in the development of lateral epicondylitis, often referred to as tennis elbow, is the impact‐induced vibration of the racket‐and‐arm system at ball contact.”

RACKET SHOCK STUDY

The study was conducted by an independent third party test facility located in Shallotte, North Carolina that specializes in medical device and sport equipment testing. OrthoKinetic Technologies, LLC, the parent company, is a leading regulatory and consulting firm specializing in regulatory and test strategies for medical devices and sport equipment.

A solid core racket dampened vibrations four times quicker with less vibratory forces than other models tested upon impact with a standardized force.

Both professional and recreational players get repetitive force transmission and vibrations to the tissues of the arm with the hits of the ball, and some of the shock is transmitted to the arm. The more prolonged the shock and vibration, the greater the risk for tissue injury.30

In the study, the solid core rackets vibrated for less than 1/5 of a second on ball contact, compared to an average of 7/10 of a second for other models tested. That means a player hitting

30 Orthokinetics 180 balls in a typical tennis match is subjected to more than 111 seconds of shock & vibration dwell time with the other brands versus a mere 32 seconds with the multi-solid core rackets. Having a shock needle in the tendon for 2 minutes can cause severe harm especially to children and minors whose tendons are not even fully developed.

The extent of frame vibration transmitted to the arm holding the racquet depends largely on how well it is dampened. Multi solid-core XeneCore construction and manufacturing process acts as a super dampener to eliminate most all of the damaging vibrations.

In, “Prediction of Impact Shock Vibrations at Tennis Player's Wrist Joint: Comparison between Conventional Weight Racket and Light Weight Racket with Super Large Head Size” in the Journal of System Design and Dynamics, the authors concluded:

“The result showed that the shock vibration of the super-light weight balanced racket with super-large sized head is much larger than that of the conventional weight balanced type racket. The result showed that the shock vibration of the super-light weight balanced racket with super-large sized head is much larger than that of the conventional weight balanced type racket.” 31

31 Kawazoe, Yoshihiko; Et al, Prediction of Impact Shock Vibrations at Tennis Player's Wrist Joint: Comparison between Conventional Weight Racket and Light Weight Racket with Super Large Head Size, Journal of System Design and Dynamics Vol. 4 (2010) No. 2 P 331‐347 RACQUET SHOCK STUDY

MULTI CORE RACQUETS VS. AIR MOLDED RACQUETS

AIR MOLDED RACQUETS TRANSMIT OVER 43,000 lbs OF FORCE PER MATCH ON THE ARM. SOLID MULTICORE RACQUETS TRANSMIT LESS THAN 14,000 lbs OF FORCE. SHOCK AMPLITUDE

BRAND 1 BRAND 2 40 Hz FREQUENCY 300 300

250 250

200 200

150 150 100 Load (N) 100 Load (N) Solid Multicore 25 Hz FREQUENCY 50 50 250 0 0 0 200 6.5 0.49 0.98 1.47 -50 5.79 7.21 7.92 -50 0.098 0.196 0.294 0.392 0.588 0.686 0.784 0.882 1.078 1.176 1.274 1.372 1.568 1.666 5.932 6.074 6.216 6.358 6.642 6.784 6.926 7.068 7.352 7.494 7.636 7.778 8.062 8.204 8.346 8.488 -100 -100 150 BRAND 3 43 Hz FREQUENCY BRAND 4 39 Hz FREQUENCY 100 Load (N) 350 250 50 300 200 0

250 0 0.48 0.96 150 1.44 0.096 0.192 0.288 0.384 0.576 0.672 0.768 0.864 1.056 1.152 1.248 1.344 200 -50 1.536 1.632 150 100 Load (N) Load (N) 100 50 50 0 0 0 -0.21 -0.22 -0.28

1.1 -50 -0.278 -0.261 -0.233 -0.252 -0.277 -0.293 -0.254 -0.206 -0.291 -0.274 -0.295 -0.244 -0.279 -0.283 -0.276

-50 0.11 0.22 0.33 0.44 0.55 0.66 0.77 0.88 0.99 1.21 1.32 1.43 1.54 1.65 1.76 -100 -100

Multi solid core racquets showed lower frequencies (25Hz) or cycles per second of vibration cycles compared to 40Hz average with the air molded racquets. This is significant as the number of oscillations corresponds to the amount of energy transmitted to the arm. If you add the amplitude of all the oscillations you will get the amount of energy transmitted to the arm in a single hit of the ball. We call this shock amplitude. In a typical match you hit the ball 180 times. If you multiply the shock amplitude by how many times you hit the ball you will find out how much energy your arm is absorbing. BRAND 1

260 250.239 250 240 230 220 210 200 190 180 170 160 150 140 130 120 110 100 90 80 70 60 50 35.389 40 30 21.318 22.823 22.058 20 12.605 13.716 16.673 13.611 11.128 12.573 11.105 10 0 -10 -205.79 5.84 5.89 5.94 5.99 6.04 6.09 6.14 -30 -40 -50

12 cycles over 0.344 seconds with a total of 604.2 newtons (135.829 pound-force) per ball hit. During a typical match this brand expells 108,756 newtons (24,449.321 pound-force) to your arm. BRAND 2

300 290 280 270 276.826 260 250 240 230 220 210 200 190 180 170 160 150 140 130 120 110 100 90 80 70 55.302 60 44.61 50 41.367 36.329 40 30 25.878 22.382 13.745 11.999 12.025 20 23.436 16.027 15.618 10.019 10 10.332 0 -10 -200.02 0.07 0.12 0.17 0.22 0.27 0.32 0.37 0.42 0.47 -30 -40 -50 -60 -70 -80 -90

15 cycles over 0.506 seconds with a total of 954.963 newtons (214.684 pound-force) per ball hit. During a typical match this brand expells 171,893.34 newtons (38,643.160 pound-force) to your arm. BRAND 3

350 340 330 320 310 300 290 298.37 280 270 260 250 240 230 220 210 200 190 180 170 160 150 140 130 120 110 100 90 74.762 80 72.151 70 64.919 52.3 60 55.076 50.769 41.65 50 40.361 35.758 40 26.045 14.257 11.989 30 27.149 10.086 20 18.143 14.982 10.639 10 0 -10 -200.02 0.07 0.12 0.17 0.22 0.27 0.32 0.37 0.42 0.47 -30 -40 -50 -60 -70 -80 -90 -100 -110

18 cycles over 0.594 seconds with a total of 1,540.442 newtons (346.305 pound-force) per ball hit. During a typical match this brand expells 277,279.56 newtons (62,334.925 pound-force) to your arm. BRAND 4

240 223.434 230 220 210 200 190 180 170 160 150 140 130 120 110 100 90 80 59.236 70 70.053 47.504 43.136 60 53.018 32.441 50 47.372 36.737 23.324 40 24.721 18.951 30 21.601 14.694 20 15.326 13.782 10 0 -10 -205.48 5.58 5.68 5.78 5.88 5.98 -30 -40 -50 -60 -70 -80 -90

16 cycles over 0.584 seconds with a total of 1,172.218 newtons (263.525 pound-force) per ball hit. During a typical match this brand expells 210,999.24 newtons (47,434.516 pound-force) to your arm. SOLID MULTI CORE

210 205 200 195 195.726 190 185 180 175 170 165 160 155 150 145 140 135 130 125 120 115 110 105 100 95 90 85 80 75 70 65 60 55 50 45 40 32.461 35 30 21.179 25 20 12.969 15 10 5 0 -5 -10 -150.02 0.07 0.12 0.17 0.22 -20 -25 -30 -35 -40 -45 -50

4 cycles over 0.16 seconds with a total of 341.13 newtons (76.689 pound-force) per ball hit. During a typical match this brand expells 61,403.4 newtons (13,804.033 pound-force) to your arm. SHOCK AMPLITUDE 1800 350000

1600 300000

1400 250000 1200

1000 SOLID MULTI CORE 200000 SOLID MULTI CORE BRAND 1 BRAND 1 800 BRAND 2 150000 BRAND 2 BRAND 3 BRAND 3 600 BRAND 4 100000 BRAND 4 400

50000 200

0 0 SOLID BRAND BRAND BRAND BRAND SOLID BRANDBRANDBRANDBRAND MULTI 1 2 3 4 MULTI 1 2 3 4 CORE CORE PER BALL HIT PER MATCH An average air molded racquet expells 1,067.955 newtons (240.086 pound-force) to your arm during a single ball hit compared to 341.13 newtons (76.689 pound-force) a solid multi core racquet expells during a single ball hit. This can be extrapolated to a typical match of 180 ball hits. The results of which would be that an average air molded racquet would expell 192,231.9 newtons (43,215.450 pound-force) to your arm during a typical match where as a solid multi core racquet would expell 61,403.4 newtons (13,804.033 pound-force) to your arm during a typical match. Over 3 times lower. METHODS

A 2.5lb weight dropped 18" along a guide to precisely hit the center of each racquet head. This is equivalent to an 80 mph tennis ball (see chart on next page). Only one bounce (shock force) was allowed for the weight. The weight did not experience a repeat hit to the center of the racquet. The center was measured for each racquet head, so it was comparable between racquets with heads of different sizes The grip was mounted to a load cell on a calibrated MTS materials test machine Since each grip varied, the grips were all mounted to the load cell in the same consistent fashion with the butt end of the grip in line with the edge of the load cell, the exposed grip to the center of the racquet head was measured for every racquet tested Tests were run for each racquet and the load vs. time continuously recorded Data was sampled at a rate of 250Hz. The distance from the center of the racquet to the exposed grip was measured for each racquet mounted. The load was directly read from the grip mounted to the load cell All rackets were strung with synthetic gut and similar tension BALL IMPACT FORMULA

Time of Impact velocity Mass of Tennis Ball Mass of Impactor t = Sqrt(2*d/g) 50 grams 1135 grams 0.11 pounds 2.5 pounds d 18 in 0.46 m g 9.8 m/s Velocity of Tennis Ball Velocity of Impactor 80 mph 3.4 mph t 0.3 s 35.7 meters/second 1.55 meters/second

Velocity of impact 1.52 meters/second Momentum of Tennis Ball Momentum of Impactor 3.35 miles/hour Mass* velocity Mass* velocity 1.79 kg*m/s 1.75 kg*m/s Available online at www.sciencedirect.com

Procedia Engineering 60 ( 2013 ) 397 – 402

6th Asia-Pacific Congress on Sports Technology (APCST) A mechanical study on tennis racquets to investigate design factors that contribute to reduced stress and improved vibrational dampening

Lisa Ferraraa*, Anders Cohenb

aOrthoKinetic Technologies, LLC., 2790 Creekbridge Ct., Southport, NC 28461, USA bBrooklyn Hospital, Dept. of Neurosurgery, 121 DeKalb Avenue, Brooklyn, NY 11201, USA Received 20 March 2013; revised 6 May 2013; accepted 3 June 2013

Abstract

upper extremities. Variations in frame design, materials, string tensioning, ball stiffness, impact locations, and player technique are just some of the potential variables that can result in a significant increase or decrease of stress transfer and vibration from the racquet to the player. To better understand the significant contributing design factors that influence shock and vibration transmission to the racquet handle upon impact, such testing was conducted in a standardized and repeatable manner to evaluate and compare the shock and vibration patterns for multiple frame designs from a variety of high performing tennis racquets. Multiple racquet frame designs from six different manufacturers were mechanically tested in an ISO17025 certified third-party independent test facility by qualified mechanical and biomechanical engineers. A consistent mass drop technique was employed to provide controlled impact to the center of the head of each mounted racquet. The impact load and duration were plotted and a Fourier Transform Analysis was conducted on each data file. The results of this study showed statistically significant reductions in vibrational dampening time and lower vibrational amplitudes following the initial impact shock for the triple core designs. This evaluation provided consistent baseline comparisons for different handle designs in a manner that demonstrated multi-layered cores of the racquet handle performed better than hollow designs with respect to vibration and force attenuation. © 2013 The Authors. Published by Elsevier Ltd. Selection© 2013 Published and peer-review by Elsevier under responsibility Ltd. Selection of theand School peer-review of Aerospace, under Mechanicalresponsibility and ofManufacturing RMIT University Engineering, RMIT University Keywords: Tennis racquet; biomechanics, handle; stress transfer; vibration; dampening; shock

* Corresponding author. Tel.: 910.253.9883. E-mail address: [email protected].

1877-7058 © 2013 The Authors. Published by Elsevier Ltd. Selection and peer-review under responsibility of the School of Aerospace, Mechanical and Manufacturing Engineering, RMIT University doi: 10.1016/j.proeng.2013.07.015 398 Lisa Ferrara and Anders Cohen / Procedia Engineering 60 ( 2013 ) 397 – 402

1. Introduction

Repetitive impact and overuse of the upper extremities in racquet sports can increase the risk of tissue fatigue and injury, leading to inflammation of the tendons and soft tissue in the wrist, elbows, and shoulders. Eventually, long term repetitive use can result in small stress fractures and chronic degeneration of the surrounding soft tissues due to microscopic tears that were incompletely healed [1]. There are many human factors such as; compromised muscular strength, poor technique, and increases in duration or intensity of play that may contribute to an increased risk of injury [2, 3]. Modern racquet designs have evolved to compensate for reduced muscular strength through the incorporation of stiffer

lead to increased shock transmission from the racquet transferred to the tissues of the upper extremities (i.e. wrist, elbow, shoulder). Additionally, prolonged exposure to vibratory oscillations due to racquet displacement has the potential to lead to fatigue injury and tissue degeneration over time [2-4]. Recently, new and innovative technologies and materials have been incorporated into the handle designs of tennis racquets in an effort to reduce shock and prolonged vibration in an effort to reduce injury to the player. Numerous variations in racquet design, materials, string tensioning, ball stiffness, impact locations, and player technique are just some of the potential variables that when combined, can result in an exponential increase or decrease of impact, stress transfer, and vibration from the racquet to the player. The specifications of a tennis racket play a large part in how the tennis racquet performs. Racquet stiffness measures its flexibility along its longitudinal axis. The stiffness is measured in terms of a rating scale, with the majority of racquets ranging between 55 and 72 on the stiffness rating scale [5, 6]. It is measured by placing a specific amount of weight on a lever, which bends the frame. A stiffer racquet will transfer greater impact energy to the tennis ball, resulting in more power, while flexible racquets return less energy, resulting in less power. The stiffness of a racquet and its relationship with energy transfer is best explained by a stress-strain curve when a tennis racquet is loaded (Fig. 1). The loading and unloading phase of a stress-strain profile generates a hysteresis curve that defines the mechanical performance of an object. Stiffness is measured as the slope of the stress-strain profile within the linear elastic portion of the curve. Therefore, when loading and unloading an object within this region, the object will undergo deformation and recover when unloaded to maintain its original shape. If an object is more compliant, greater deformation will occur during loading, resulting in a wider hysteresis curve and greater energy loss (Fig. 1a). The hysteresis curve is the sigmoidal curve generated from loading and unloading of an object (Fig. 1b). The area within this curve represents the energy loss. A wider curve represents greater energy loss and is indicative of an object with greater compliance or flexibility. A narrow curve is indicative of a stiffer object. If less energy is lost during the loading and unloading of an object, the hysteresis curve would be narrow when compared to the current graph shown in Fig. 1a. If less energy is lost, the remainder of energy will be directly transferred to the object, thus resulting in higher stress transfer to the object. In essence, a stiffer racquet that has less energy loss will transfer higher stresses from the handle to the tissue gripping the handle. Furthermore, a stiffer racquet will transfer greater impulse forces (shock) [5, 6] to the human tissue, and higher vibratory amplitudes. Lower amplitudes and shock forces indicate greater flexibility. Many studies have investigated a combination of these variables to quantify shock and/or vibration for a variety of racquet designs. However, variations in the literature exist with respect to study design where controlled comparative studies were difficult to perform, included a multitude of variables that may have masked the study outcomes, and may have provided conflicting or inconclusive comparisons. To better understand the significant contributing factors towards stress and vibration transfer for different tennis racquet frame designs, such testing was conducted in a standardized, consistent, and repeatable manner to provide statistically valid comparisons with minimized variability in the study design. Therefore, the goal Lisa Ferrara and Anders Cohen / Procedia Engineering 60 ( 2013 ) 397 – 402 399 of the present study was to provide an initial mechanical evaluation of shock and vibration for multiple frame designs from a variety of high performing tennis racquets to investigate potential design factors that could influence shock and vibration transmission to the racquet handle upon impact. In order to provide a direct comparison between racquet handle designs, the testing conducted was controlled in a manner to isolate specific design factors and eliminate the effects of string material and tension.

Yield Stress

Elastic Limit

Ultimate Strength Stiffness STRESS (slope)

Elastic Region Plastic Region Will not recover to original shape Will recover to original shape

STRAIN (a)

STRESS Loading

Unloading

STRAIN (b)

Fig. 1. Relationship between stiffness and energy through stress-strain curves (a); Typical hysteresis curve (b)

400 Lisa Ferrara and Anders Cohen / Procedia Engineering 60 ( 2013 ) 397 – 402

2. Materials and methods

Ten racquet frame designs from five different manufacturers were mechanically tested in an ISO17025 certified third-party independent test facility by qualified mechanical and biomechanical engineers. To minimize variability and provide a well-controlled comparison between tennis racquets, a consistent mass drop technique using a calibrated mass along a drop guide mounted to an electromechanical materials test machine (MTS Corp. Eden Praire, MN) was employed to provide accurate repetitive impact to the center of the head of each mounted tennis racquet. The center was determined through direct measurements and marked for each specific racquet tested. Each racquet handle was secured to a load cell (maximum capacity of 5kN) via gripping plates such that the face of the racquet was perpendicular to the mounted handles. A 2.5lb (11N) weight was dropped at 18 inches

impact. The mean accel et in swing motion impacting a tennis ball with a collision duration of 5ms [6]. The specifications for each racquet, string tension, total handle length, and exposed handle length from the fixed edge of each mounted racquet were recorded. To minimize variability for consistency, the exposed handle length was maintained within the same ratio with respect to the total handle length for the different manufacturers and the string tensions were set to manufacturer specifications. The results were evaluated between racquet handle designs for both normalized and non-normalized of the parameters to the string tension for pr measured parameter (peak force) were divided by its string tension and statistically compared. This was conducted to remove the variability created by the slightly varied string tensions between tennis racquets for statistical comparisons. The composition and design of each handle was also documented and necessary for the comparative analysis. There were three different types of handles designed (triple core, dual core, hollow) and are outlined in Table 1, which detail the specifications for each racquet type. The internal core designs of the handle were categorized as the triple core, dual core, or hollow design. Force and dampening times were compared with and without normalization to the string tension. Furthermore, the mounting of the racquets and design of the study minimized such variabilities due to the consistent nature of the test design. Each racquet handle was mounted and rigidly affixed to a calibrated load cell mounted to a materials test machine. The length of the exposed handle to the marked center of the racquet head was measured and the ratio of exposed length to total length to the center was maintained for all of the racquets tested. Five impact tests per racquet were performed. The impact and vibratory forces and duration were continuously sampled using MTS Testworks Software and a Fourier Transform Analysis was conducted on each data file sampled. This allowed for the full sinusoidal oscillation patterns to be sampled and the force at impact, force for each vibration, and time to dampen to be analyzed. The Fourier Transform generated the time domain and frequency domain for each sample. Minimizing variability from the impacting element, impact location, and the string tension in the manner described above allowed for a direct comparison between racquets to better determine the contributing factors towards stress reduction and vibration dampening from the handle of the racquet to the player. The time domain, initial impact force and vibratory forces transferred to the handle, and vibratory duration (time to reduce oscillations to a negligible force <5N) were analyzed. Dampening was considered complete when the vibrational amplitudes (in terms of force) were less than 5N. A one way Analysis of Variance (ANOVA) to a confidence interval of 95% and paired two-tailed t-tests were conducted to identify differences between the racquet handle designs.

Lisa Ferrara and Anders Cohen / Procedia Engineering 60 ( 2013 ) 397 – 402 401

Table 1. Racquet parameters categorized by handle design

Racquet Number Material Handle Design Stiffness Rate 1 Carbon Fiber Triple core 61 2 Graphite Dual core 63 3 Carbon Fiber Triple core 57 4 Graphite Dual core 64 5 Graphite Dual core 61 Mean (Stdev) 61.2 (2.7) 6 Graphite w basalt planks Hollow 68 7 Graphite Tungsten Hollow 67 8 Graphite Hollow 70 9 Graphite Hollow 67 10 Graphite Tungsten/Copper/Titanium Hollow 65 Mean (Stdev) 67.4 (1.8)

3. Results

Table 1 showed that the stiffness between the racquet types were lower for the core handle design group when compared to the hollow handle. Statistically the dual and triple core racquets were significantly less stiff than the hollow racquets (p<0.05) as shown in Table 1. The time to dampen the vibrations was greatest for the hollow racquets. Contrary to this, the triple core demonstrated the shortest dampening time with respect to the vibratory oscillations. Additionally, the hollow racquets demonstrated greater peak force (shock) than the triple and dual core, with the triple core demonstrating the fastest vibration dampening, lowest shock force, and lowest vibratory forces transmitted to the racquet handles (Figures 2a through 3a). The Fourier Transform analysis demonstrated significant reductions in the vibrational dampening from the generated time domains for the core handle designs greater than the hollow designs. Additionally, the amplitudes during the vibration oscillations following the initial shock impulse for the core handle design were significantly less than that for the hollow designs, with the triple core handle design demonstrating the greatest decrease in amplitude after the initial shock force, P<0.05, (Fig. 2b). The hollow core design reduced shock force by 22%, where the core designs reduced the shock by at least 65% or more.

Hollow Core Hollow Core

Dual Core Dual Core

Triple Core Triple Core

0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 200 210 220 230 240 250 260 270 Vibration Dampening Time [sec] Shock Force [N]

Fig. 2. (a) Mean vibration dampening time at impact for the handle design; (b) Mean shock force at impact for the handle design 402 Lisa Ferrara and Anders Cohen / Procedia Engineering 60 ( 2013 ) 397 – 402

hollow hollow Hollow hollow hollow hollow Dual dual C dual B dual A Triple 1st Peak triple B 2nd Peak triple A 0 50 100 150 200 250 300 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 Peak Force [N] Vibration Dampening Time [sec]

Fig. 3. (a) Vibration dampening times per racquet handle design; (b) Force difference between impulse and 2nd vibratory force

4. Conclusions

The dual and triple core designs demonstrated reduced dampening time where these designs successfully dampened the vibratory oscillations by at least 35% for the dual core and 50% for the triple core design when compared to the hollow handle design. Additionally, the amplitudes during the vibration oscillations following the initial shock impulse force for the core handle design were significantly less than that for the hollow designs, with the core handle designs demonstrating a reduction in these forces by at least 65% and the hollow core design reducing the shock force by 22% (Fig. 3b). Overall, the dual and triple core designs demonstrated significantly lower shock forces and vibratory forces and dampened vibration quicker than the hollow designs. Although this study provided a controlled and repeatable assessment of racquet design, additional testing is currently underway to further investigate the impact of design factors that have the greatest capacity to reduce shock and vibration while replicating tennis swing kinematics and upon ball impact.

References

[1] Regan WD, Grondin PP, Morrey BF. Elbow and forearm. In: DeLee JC, Drez D Jr., Miller MD, eds. DeLee and Drez's Orthopaedic Sports Medicine. 3rd ed. Philadelphia, Pa: Saunders Elsevier; 2009:chap 19. [2] William C. Whiting PhD; Ronald F. Zernicke PhD, Biomechanics of Musculoskeletal Injury, Second Edition ISBN-10: 0736054421, ISBN-13: 978-0736054423. [3] Nordin M, Frankel, VH., Basic Biomechanics of the Musculoskeletal Skeletal System, 2nd edition, Williams and Wilkins, Lippincott, Philadelphia, PA, ISBN 0-683-30247-7. [4] Reynolds DD, Standlee KG, Angevine EN, Hand-Arm Vibration, Part III: Subjective Response Characteristics of Individuals to Hand-Induced Vibration, Jour. Of Sound and Vibration, 1977, 51(2); pp:267-282. [5] Miller S, Modern Tennis Rackets, Balls, Br. J. Sports Med. 2006; 40:401-405, bjsm:2005.023283. [6] Brody H, Cross R, Lindsey C, The Physics and Technology of Tennis, Independent Pub Group, April 2004, ISBN-13 9780972275903, ISBN-10-0972275908. 3/21/2020 Tissue Stress Magnitude – An Independent Study in Search of Arm Friendly Tennis Racquets

Tissue Stress Magnitude – An Independent Study In Search Of Arm Friendly Tennis Racquets Home  Tissue Stress Magnitude – An Independent Study In Search Of Arm Friendly Tennis Racquets

Over the years, Donnay has established a brand that focuses on producing arm friendly tennis racquets. I reached out to Donnay asking couple questions, about the methods, approach on design etc… when asked about the performance and a scientic stufy, they provided the independent study by Orthokinetic Labs, which Im posting below unedited.

https://donnaytennis.com/tissue-stress-magnitude-an-independent-study-in-search-of-arm-friendly-tennis-racquets 1/3 3/21/2020 Tissue Stress Magnitude – An Independent Study in Search of Arm Friendly Tennis Racquets

The results of the rst part of the rst-ever independent Racket Shock & Injury Medical Study are in and they dramatically show that Donnay multi-solid core frames produce four times less shock & vibration time on ball contact than competitive hollow rackets from the four leading brands.

The study was conducted by OrthoKinetic Technologies, LLC, a leading independent rm in Shallotte, NC, that tests medical devices for regulatory and pre-clinical test strategies for FDA and CE submissions.

The Donnay racket, engineered for Arm Safe Performance, vibrated for less than 1/5 of a second on ball contact in the test, compared to an average of 7/10 of a second for the other models tested. That means a player hitting 180 balls in a typical tennis match is subjected to more than 111 seconds of shock & vibration dwell time with the other brands versus 32 seconds with the Donnay.

The importance of the study to players: They get a vibration every time they hit the ball and some of the shock is transmitted to the arm. The more prolonged the shock & vibration the more it can cause arm injuries. Results of the second part of the study – the amount of initial shock & vibration between Donnay and the other brands will be released next week.

The extent of frame vibration transmitted to the arm holding the racquet depends largely on how well it is dampened. Donnay’s solid- core XeneCore construction and manufacturing process acts as a super dampener to eliminate most all of the damaging vibrations.

In the old wood rackets, vibration disappeared quickly because it was dampened by the ex of the solid wood, but the new stiffer, lighter and hollow conventional frames do a poor job of snufng out the vibrations, so they transfer this shaking to the arm that can stealthily sabotage the elbow, wrist, forearm and shoulder. The longer the vibration and the longer a player rallies the more the tendons are stressed. This constant stressing is how a coathanger is broken by bending it back and worth. Eventually, fatigue can cause tissues to snap, even without any tremendous force.

Hollow racquets with their poor dampening properties cause pain (think of hitting a with the hollow aluminum baseball bat on a chilly day).

https://donnaytennis.com/tissue-stress-magnitude-an-independent-study-in-search-of-arm-friendly-tennis-racquets 2/3 3/21/2020 Tissue Stress Magnitude – An Independent Study in Search of Arm Friendly Tennis Racquets

For years the tennis industry has laid the blame for arm injuries on poor stroking techniques, conveniently diverting scrutiny from the design of racquets, but hollow, stiff, ultralight head-heavy racquets are more to blame. As conventional racquets have grown lighter and stiffer the number of players suffering from arm and elbow pain has also risen dramatically. The cause is no longer primarily related to mechanics, but rather to the equipment itself.

In addition to Donnay’s solid-core technology and consistent with its mantra of “Arm Safe Performance,” Donnay’s specs reect more arm-friendly properties that include more mass, head-light balances and exible frames.

The release of the rst part of the study, entitled “Tissue Stress Magnitude,” is great news for your retail dealers since as many as one- in-four of their customers are currently experiencing some form of arm pain and are looking for racquets that help them recover quickly or play through the pain. That’s when power and control take a backseat.

Because if you’re trying to play hurt, you’re not playing well at all.

Best wishes for the holidays and we’ll keep you breast with the rest of the study, along with a detailed report from next week from OrthoKinetic Technologies.

https://donnaytennis.com/tissue-stress-magnitude-an-independent-study-in-search-of-arm-friendly-tennis-racquets 3/3

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